USB: chipidea: add -DDEBUG if debugging is enabled

This patch turns on debugging output if CONFIG_USB_CHIPIDEA_DEBUG is
enabled.

Signed-off-by: Richard Zhao <richard.zhao@freescale.com>
Tested-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Tested-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>